Test 1 and Test 2 will have questions which check your knowledge of project management theory and PMBOK : these will help identify your weak areas for further study
Test 3 has situational questions and is very similar to final CAPM exam
Test 4 covers concepts (and has repetitions) from questions covered in Test 1, Test 2 and Test 3. It is very good practice after completing Test 1, Test 2 and Test 3 and should be taken before final CAPM Exams
Guides on all the knowledge areas which includes :
Important Terms and Concepts for all the knowledge areas (to be used as flashcards)
Study Guides on all knowledge areas which highlight areas where most questions are possible
For cost management and time management knowledge areas, study guides about mathematical questions